LM95234_07 NSC [National Semiconductor], LM95234_07 Datasheet - Page 10

• Manufacturer Part Number: LM95234_07
• Description: Quad Remote Diode and Local Temperature Sensor with SMBus Interface and TruTherm Technology
• Manufacturer: NSC [National Semiconductor]

www.national.com
1.0 Functional Description
LM95234 is an 11-bit digital temperature sensor with a 2-wire
System Management Bus (SMBus) interface that can monitor
the temperature of four remote diodes as well as its own tem-
perature. The LM95234 can be used to very accurately mon-
itor the temperature of up to four external devices such as
microprocessors, graphics processors or diode-connected
2N3904 transistor. The LM95234 includes TruTherm BJT be-
ta compensation technology that allows sensing of Intel pro-
cessors 90 nm or 65 nm process thermal diodes accurately.
The LM95234 reports temperature in two different formats for
+127.875°C/–128°C range and 0°C/255°C range. The
LM95234 has a Sigma-Delta ADC (Analog-to-Digital Con-
verter) core which provides the first level of noise imunity. For
improved performance in a noisy environment the LM95234
includes programmable digital filters for Remote Diode 1 and
2 temperature readings. When the digital filters are invoked
the resolution for Remote Diode 1 and 2 readings increases
to 0.03125°C. The LM95234 contains a diode model selection
register that includes bits for each channel that select be-
tween thermal diodes of Intel processors on 65 nm process
or 2N3904s. For maximum flexibility and best accuracy the
LM95234 includes offset registers that allow calibration of
other diode types.
Diode fault detection circuitry in the LM95234 can detect the
absence or fault state of a remote diode: whether D+ is short-
ed to V
The LM95234 TCRIT1, TCRIT2 and TCRIT3 active low out-
puts are triggered when any unmasked channel exceeds its
corresponding programmable limit and can be used to shut-
down the system, to turn on the system fans or as a micro-
controller interrupt function. The current status of the
TCRIT1, TCRIT2 and TCRIT3 pins can be read back from the
status registers via the SMBus interface. Two of the remote
channels have two separate limits each that control the
TCRIT1 and TCRIT2 pins. The remaining two channels and
the local channel each have one limit to control both the
TCRIT1 and TCRIT2 pins. The TCRIT3 pin shares the limits
of the TCRIT2 pin but allows for different masking options. All
limits have a shared programmable hysteresis register.
Remote Diode 1 and 2 temperature channels have pro-
grammable digital filters while the other two remote temper-
ature channels utilize a fault-queue in order to avoid false
triggering the TCRIT pins.
LM95234 has a three-level address pin to connect up to 3
devices to the same SMBus master. LM95234 also has pro-
grammable conversion rate register as well as a shutdown
mode for power savings. One round of conversions can be
triggered in shutdown mode by writing to the one-shot register
through the SMBus interface. LM95234 can be programmed
to turn off unused channels for more power savings.
The LM95234 register set has an 8-bit data structure and in-
cludes:
1.
2.
Temperature Value Registers with signed format
— Most-Significant-Byte (MSB) and Least-Significant-
— MSB and LSB Remote Temperature 1
— MSB and LSB Remote Temperature 2
— MSB and LSB Remote Temperature 3
— MSB and LSB Remote Temperature 4
Temperature Value Registers with unsigned format
— MSB and LSB Remote Temperature 1
— MSB and LSB Remote Temperature 2
DD
Byte (LSB) Local Temperature
, D- or ground, or whether D+ is floating.
10
3.
4.
5.
6.
7.
8.
9.
1.1 CONVERSION SEQUENCE
The LM95234 takes approximately 190 ms to convert the Lo-
cal Temperature, Remote Temperatures 1 through 4, and to
update all of its registers. These conversions for each thermal
diode are addressed in a round robin sequence. Only during
the conversion process the busy bit (D7) in Status register
(02h) is high. The conversion rate may be modified by the
Conversion Rate bits found in the Configuration Register
(03h). When the conversion rate is modified a delay is insert-
ed between each round of conversions, the actual time for
each round remains at 190 ms (typical all channels enabled).
The time a round takes depends on the number of channels
that are on. Different conversion rates will cause the LM95234
to draw different amounts of average supply current as shown
in Figure 1. This curve assumes all the channels are on. If
channels are turned off the average current will drop since the
round robin time will decrease and the shutdown time will in-
crease during each conversion interval.
— MSB and LSB Remote Temperature 3
— MSB and LSB Remote Temperature 4
Diode Configuration Registers
— Diode Model Select
— Remote 1 Offset
— Remote 2 Offset
— Remote 3 Offset
— Remote 4 Offset
General Configuration Registers
— Configuration (Standby, Fault Queue enable for
— Channel Conversion Enable
— Filter Setting for Remote 1 and 2
— 1-Shot
Status Registers
— Main Status Register (Busy bit, Not Ready, Status
— Status 1 (diode fault)
— Status 2 (TCRIT1)
— Status 3 (TCRIT2)
— Status 4 (TCRIT3)
— Diode Model Status
Mask Registers
— TCRIT1 Mask
— TCRIT2 Mask
— TCRIT3 Mask
Limit Registers
— Local Tcrit Limit
— Remote 1 Tcrit-1 Limit
— Remote 2 Tcrit-1 Limit
— Remote 3 Tcrit Limit
— Remote 4 Tcrit Limit
— Remote 1 Tcrit-2 and Tcrit-3 Limit
— Remote 2 Tcrit-2 and Tcrit-3 Limit
— Common Tcrit Hysteresis
Manufacturer ID Register
Revision ID Register
Remote 3 and 4; Conversion Rate)
Register 1 to 4 Flags)